The Sixteen Personality Factor Questionnaire (or 16PF)[1], is a multiple-choice personality questionnaire which was scientifically developed over several decades of research by Raymond B. Cattell and his colleagues. Beginning in the 1940s, Cattell used the newly emerging techniques of factor analysis (based on the correlation coefficient) in a quest to try to discover all the fundamental dimensions of human personality[2]. Thus, the 16PF Questionnaire was empirically developed to comprehensively measure all of the basic traits of normal personality[3].

In addition to the sixteen primary traits, these researchers also discovered five "second-order" traits of personality now known as the Big Five[4], which have recently become popularized. From early in his research, Cattell found the structure of personality to be multi-level or hierarchical, with both primary and secondary level traits[2][5]. The sixteen primary factors were a result of factor-analyzing hundreds of ratings of everyday behaviors to find the structure behind them. Next, five global (or second-order) factors were discovered by factor-analyzing the sixteen primary traits. Thus, the 16PF provides scores on both the second-order global traits which provide an overview of personality at a higher, broad-brush, conceptual level, as well as the more precise primary traits, which reveal the fine details of each unique personality. A listing of these traits can be found in the article on the 16 Personality Factor Model. Cattell also found that there was a third-order level of personality organization that contained just two over-arching, top-level factors [2][6], but less time was spent on defining this most abstract level of personality organization.

Because of its scientific origins, the 16PF has a long history of empirical research, and is embedded in Cattell's comprehensive theory of individual differences. The test's 60 years of research have shown it to be effective in a variety of settings where an in-depth, integrated understanding of the whole person is needed. It is used in schools and colleges, clinical and counseling settings, career counseling and employee selection and development, as well as in basic personality research. The test has been found to predict a wide range of important behaviors, such as creativity, academic achievement, cognitive style, empathy and interpersonal skills, leadership potential, conscientiousness, self-esteem, frustration tolerance, coping patterns, marital compatibility, and job performance[7][8][9]. The test is widely used internationally. It has been translated and adapted into over 35 languages and dialects.

Cattell and his colleagues also developed parallel personality questionnaires to measure traits across the age-ranges, such as the Adolescent Personality Questionnaire for ages 12 to 18 years[10]. A shorter version, the 16PF Select Questionnaire, has been developed for personnel settings [11]. Cattell also developed measures of ability, such as three scales of the Culture-Fair Intelligence Test[12] and tests of motivation. These tests are available from IPAT.com.

The most recent edition of the Sixteen Personality Factor Questionnaire (16PF) is the fifth edition of the test[13]. The test was originally published in 1949; the second and third editions were published in 1956 and 1962, respectively; and the fourth edition had five alternative forms which were released between 1967 and 1969. The fifth edition revision was aimed at updating, improving, and simplifying the language used in the test; simplifying the answer format; creating new validity indices; improving the psychometric properties of the test, including new reliability and validity data; and developing a new standardization sample that reflects the current U.S. Census population.

The 16PF Fifth Edition consists of 185 multiple-choice items which are written at a fifth-grade reading level. The item content is non-threatening and asks simple questions about daily behavior, interests, and opinions. Administration of the test takes about 35-50 minutes for the paper-and-pencil version and about 30 minutes by computer. Because the test instructions are simple and straightforward, and the test is untimed, it is virtually self-administrable and can be given in either an individual or a group setting.

The 16PF Questionnaire was designed to be administered to adults approximately age 16 and older, but there are parallel tests for various younger age ranges (e.g., the 16PF Adolescent Personality Questionnaire[14]). The test provides scores on sixteen primary scales (one of which is a brief ability scale), five global scales, and three validity scales. All personality scales are bipolar, meaning that both ends of each scale have a clear, meaningful definition.

The 16PF Questionnaire has been translated into more than 35 languages and dialects worldwide. Thus the test can be administered in many different languages, scored with a local national normative sample for that particular language group, and reported in over a dozen different languages. The test has been culturally adapted in these countries, with standardization samples plus reliability and validity information collected locally and presented in the manuals.

The 16PF Questionnaire can be hand-scored using a set of scoring keys, or computer-scored by mailing or faxing the answer sheet to the Publisher IPAT". The test can also be administered and scored using a software system or using an internet-based system, which provides administration in many different languages. There are numerous computer-generated interpretive reports which can be used to help interpret the test for different purposes, for example, the Personal Career Development Profile, the Karson Clinical Report, The Couples Counseling Report, the Human Resource Development Report, the Data Summary Report, the Teamwork Development Report, and the Leadership Coaching Report. There are also many books available that help with test interpretation, for example, 16PF Interpretation in Clinical Practice (Karson, Karson, & O'Dell, 1997)[15], The 16PF: Personality in Depth (Cattell, H.B.,1989)[16], or Essentials of the 16PF (Cattell, H.E. & Schuerger, J.M, 2003)[17].

A shorter version of the test, the 16PF Select (Cattell, Cattell, Cattell & Kelly, 1999)[18], was developed specifically for use in employee selection settings, and involves a subset of the items and scales in the regular test. The 16PF Express (Gorsuch, 2007)[19] provides a very short, 15-minute, version of the test for research purposes, which has about four items per factor and a different answer-format. The 16PF traits are also included in the PsychEval Personality Questionnaire (PEPQ), which combines measures of both normal and abnormal personality dimensions into one test (Cattell, Cattell, Cattell & Russell, 2003)[20]